Self-regulatory phenomena in plant development

Abstract

Every living organism has the power to produce structures, and to carry on activities, which cannot be regarded as consequences of the environment. The whole science of taxonomy rests upon the steady persistence with which each species adheres to its own characteristic scheme of development. Used with discretion any taxonomic work will furnish us with a select list of developmental processes which experience has shown to be, over a wide range, independent of environmental influence. All these processes must be considered to display the quality of self-regulation. We need not suppose that physiological systems which are in this sense self-regulating are necessarily inaccessible to experimental treatment. The very fact that a plant has survived indicates that its developmental physiology can bear wind and weather, the passage of the seasons, and accidental inequalities of nutrition. It follows therefore that to obtain significant experimental results we ought to resort to treatments which are quite outside the range of the plant’s normal experience. The fact, for example, that an ordinary crucifer will continue to produce dimerous flowers under any conditions which will permit it to flower at all, is sufficient guarantee that we are unlikely to learn anything of the underlying physiology by gentle photoperiodic stimulation, or anything of that kind. But there is nothing irrational in the supposition that the symmetry of the flower might admit of instructive modification if the primordium were centrifuged or subjected to electrical treatment. And if some “unnatural” treatment were to be discovered which would cause the flowers to develop in trimerous form that need not alter our view regarding the self-regulating quality of the normal mode of development.